Solid Mechanics Analysis Research Articles

Vitreous tissue cryopreservation using a blood vessel model and cryomacroscopy for scale-up studies: Observations and mathematical modeling

Successful long-term cryobanking of multicellular tissues and organs at deep subzero temperatures calls for the avoidance of ice cryoinjury by reliance upon ice-free cryopreservation techniques. However, the quality of the cryopreserved material is the direct result of its ability to survive a host of harmful mechanisms, chief among which is overcoming the trifecta effects of ice crystallization, toxicity, and mechanical stress. This study aims at exploring improved conditions to scale-up ice-free cryopreservation by combining DP6 as a base cryoprotective agent (CPA) solution with an array of synthetic ice modulators (SIMs). This study is conducted by integrating cryomacroscopy techniques, thermal modeling, solid mechanics analysis, and viability and contractility investigation to correlate physical effects, thermal outcomes, and cryobiology results. As an extension of previous work, this study aims at scale-up of established baseline blood vessel models, while comparing the relative toxicity and vitreous stability of 4 ml and 10 ml samples of DP6 containing either sucrose as a SIM, or the commercial synthetic ice blockers (X1000 and Z1000). Using that established protocol, the addition and removal of DP6+0.6M sucrose and DP6 + 1% X1000 + 1% Z1000 were both well tolerated in rabbit carotid and pig femoral artery models, when assessed for metabolic recovery and contractility. Using cryomacroscopy, it was demonstrated that DP6 + 0.6M sucrose provided a stable vitrification medium under marginal cooling and warming conditions that resulted in >50% survival rate. By contrast, DP6 + 1% X1000 + 1% Z1000 was subject to visible ice formation during cooling under the same thermal conditions, resulting in a significantly lower recovery of ∼20%. Thermal modeling is used in this study to verify the actual cooling and rewarming rates in the specimens, while thermomechanics analysis is used to explain why fractures were observed using cryomacroscopy when the specimens were contained in glass vials but not in plastic vials.

The modified physics-informed neural network (PINN) method for the thermoelastic wave propagation analysis based on the Moore-Gibson-Thompson theory in porous materials

This paper presents novel contributions to both theory and solution methodology in AI-based analysis of solid mechanics. The physics-informed neural network (PINN) method is developed for thermoelastic wave propagation and Moore-Gibson-Thompson (MGT) coupled thermoelasticity analysis of porous media, a first in the field. The coupled thermoelasticity governing equations, based on the MGT heat conduction model, are derived for a porous half-space, with the thermal relaxation coefficient and strain relaxation factor being considered. Mechanical and thermal shock loading boundary conditions are imposed. The behavior of a magnesium-made porous body is analyzed using the PINN method, with highly accurate results being achieved for the system of coupled PDEs. An adaptive hyperparameter tuning approach, integrating a generalized subset design (GSD) and Bayesian optimization algorithm, is used to automatically select the optimal structure based on the L2 relative error. This hybrid methodology eliminates manual adjustment concerns. The proposed method is verified through a thorough comparison with the Lord-Shulman theory of coupled thermoelasticity. The strength of the methodology lies in its ability to operate without domain data, with only boundary and initial points being required. Four example sets are examined to demonstrate the capabilities of the modified PINN, and high-quality predictions of dimensionless fields’ variables over an extended time interval are obtained, confirming its extrapolation abilities.

Simulation study on the effect of eccentricity on the performance of a reciprocating seal

This article establishes a three-dimensional fluid-structure interaction (FSI) model for reciprocating rod seals. Based on this model, a novel method using a two-dimensional FSI model to solve the average sealing performance across multiple sections is proposed for the first time. This method allows for the dimensional reduction of solid mechanics, contact mechanics, and fluid mechanics analysis. The performance of the sealing system was calculated and analyzed under static eccentricity (which does not change with piston rod motion) and dynamic eccentricity (which changes with piston rod motion) using the aforementioned models. The results indicate that the sealing performance calculated by both models is highly consistent, demonstrating that, within the permissible engineering limits, the two-dimensional FSI model can replace the three-dimensional model, thereby reducing computational costs and improving convergence. Additionally, the results show that eccentricity increases the friction and leakage rates of the sealing system, with dynamic eccentricity having a greater impact on sealing performance than static eccentricity due to the viscoelasticity of the rubber.

Solid-mechanics analysis and modeling of the alloyed ohmic contact proximity in GaN HEMTs using µRaman spectroscopy

This study explores the impact of alloyed ohmic contact separation on ungated GaN high electron mobility transistors (HEMTs) lattice stress by employing Raman spectroscopy and solid mechanics simulations for comprehensive analysis. Focusing on the substantial stresses exerted by ohmic contacts, our research introduces a novel mechanical calibration procedure. The proposed procedure demonstrates that the stress in the GaN buffer can be precisely modelled using Raman measurements taken from patterns of varying length, which in return reveals the impact of ohmic contacts on stress. We show that this technique shows a good alignment to the Raman measurement results. Moreover, we identify ohmic contact edges as potential sites for defect generation due to the accumulation of substantial elastic energy, a finding supported by experimental observations of crack formations in related studies. Our calibrated mechanical model not only enhances the understanding of stress distributions within GaN HEMTs but also lays the groundwork for future improvements in electro-thermo-mechanical simulations.

Enhancing the Thermal Performance of Shape Memory Polymers: Designing a Minichannel Structure.

This research proposes a numerical approach to improve the thermal performance of shape memory polymers (SMPs) while their mechanical properties remain intact. Sixteen different 3D minichannel structures were numerically designed to investigate the impact of embedded water flow in microchannel networks on the thermal response and shape recovery of SMPs. This work employs two approaches, each with different physics: approach A focuses on solid mechanics analysis and, accordingly, thermal analysis in solids without considering the fluid. approach B tackles solid and fluid mechanics analysis and thermal analysis in both solid and fluid subdomains, which inherently calls for fluid-structure coupling in a uniform procedure. Finally, the results of these two approaches are compared to predict the SMP's thermal and mechanical behavior. The structural designs are then analyzed in terms of their shape recovery speed, recovery ratio, and recovery parameters. The results indicate that isotropic structures thermally outperform their anisotropic counterparts, exhibiting improved thermal characteristics and faster shape recovery. Additionally, it was observed that polymeric structures with a low volume fraction of embedded branches thermally perform efficiently. The findings of this study predict that the geometrical angle between the main branch and sub-branches of SMP favorably impacts the enhancement of thermal characteristics of the structure, accelerating its shape recovery. Approach B accelerates the shape recovery rate in SMPs due to fluid flow and uniform heat transfer within the structures.

Combining fracture mechanics and rheology to investigate the impact of micro-aeration on chocolate oral processing.

This study presents a rigorous mechanical characterisation investigation on milk chocolate with varying porosities, at different temperatures and strain rate levels. Uniaxial compression tests at temperatures varying from 20 °C to 30 °C were performed to measure the bulk properties of chocolate as a function of porosity and temperature. Fracture experiments were also conducted to compute the fracture energy at temperature levels between 20 °C and 30 °C for all tested samples. Additionally, rheological experiments are conducted to compute the viscosity of the different chocolates at 37 °C. This combined experimental analysis of solid mechanics, fracture mechanics, and rheology aims to define the impact of temperature and chocolate's phase change from solid to liquid on its mechanical properties. Moreover, the impact of micro-aeration on the relationship between material properties and temperature is discussed. The results demonstrate a significant impact of both temperature and micro-aeration on the chocolate's material properties; fracture stresses decrease with micro-aeration due to the presence of micro-pores creating weak links in the chocolate matrix, the critical strain energy release rate decreases with micro-aeration at temperatures up to 25 °C and increases at temperatures above 30 °C. Finally, the viscosity at 37 °C increases with increasing porosity due to the obstruction of the flow by micro-pores acting as "solid" particles. The results highlight how the impact of micro-aeration on the material properties of chocolate alters as the testing temperature rises and the material changes phase. The relationships between the micro-aeration and material properties and the dependence of temperature on the different mechanical properties are used to explain the difference in textural attributes as obtained from temporal dominance sensation tests. This study seeks to contribute valuable insights into the field of chocolate technology, emphasizing the need for a combined engineering approach to understand the structural breakdown of chocolate during oral processing as mechanisms such as chewing, melting, mixing and shearing occur.

Structural design of solar car body based on solid mechanics analysis of solar panel surface

With the increasingly serious problem of global warming and the growing scarcity of energy represented by oil, automobile development has reached a historical tipping point. Nowadays, the most popular solution is to use other clean and sustainable energy to replace current oil and natural gas, thereby addressing both environmental and energy shortage issues. Solar energy, as a "inexhaustible" source of energy, has made significant technological advances over the course of human history. There is, however, a gap in the application of solar energy technology in automotive technology. This paper uses COMSOL software to model the most commonly used solar panels and simulates and studies the streamline distribution, velocity distribution, pressure distribution, and stress distribution of the solar surface under high-speed movement of 90km/h. SoildWorks simulation is used to design a vehicle body structure for future solar cars based on these data. FLUENT software is used to simulate and study the streamline distribution and pressure distribution of the car body at a high speed of 90km/h. Finally, the design's logic and feasibility are validated. The fluids on the surface of a single solar panel and a vehicle body are simulated in this paper. Testing the pressure distribution and stress and strain tests can reveal the rationality and feasibility of the structural design.

Leakage Analysis of PEMFC Sealing System Considering Temperature Cycling

Addressing the leakage rate prediction problem of the PEMFC sealing system is of great importance for its stable operation. The leakage calculation method of the PEMFC sealing system is proposed based on thermal coupling. The parallel plate leakage model is improved to make it applicable to the leakage rate calculation with a variable channel cross-section height. The interface macroscopic contact pressure is solved using a finite element simulation for solid mechanics analysis. The Greenwood–Williamson model is used for contact mechanics analysis to solve for the average height of the leakage channel. The effects of the ambient temperature, compression ratio, bipolar plate misalignment, and gasket size on the cell sealing effect were studied numerically. The data indicated that as the ambient temperature, compression ratio, and gasket size became larger, the volume leakage rate began to be reduced. The leakage rate as a parameter to characterize the sealing performance, considering the influence of gasket size, operating conditions, and other factors on the cell sealing effect, is more meaningful for the durability study and failure analysis of PEMFC.

Effect of offset between beam outside and neutral surfaces on dynamic soil-structure interactions

In finite element analyses of the dynamic soil-structure interaction (SSI), structures are often modelled as beam or shell elements in structural mechanics, while the soil requires discretization using solid elements in solid mechanics. The beam and shell elements are coupled with the solid elements on their outer surfaces, while the mechanical behaviour of the beam and shell elements are usually represented by variables defined at their neutral surfaces. The offset between the beam outer surface and the neutral surface in several dynamic SSI analyses is often ignored, which can cause large errors in the coupling analysis of solid and structural mechanics. This paper investigates the effect of the offset between the beam outer surface and neutral surface on the dynamic SSIs. First, the coupling conditions between the beam and the solid considering the offset between the beam outer surface and the neutral surface are deduced. In this process, the tangential interaction stress on the beam outer surface is transformed into an axial force and a moment acting on the beam neutral surface, and the tangential displacement on the beam outer surface is related to the axial displacement at the beam neutral surface as well as the cross-section rotation angle. Then, the coupling condition is implemented in the finite element analysis by modifying the mass and stiffness matrices of the beam element. The offset effects between beam outer surfaces and neutral surfaces on dynamic SSIs are finally discussed in detail through the seismic responses of a retaining wall, subway station and tunnel.

Numerical simulation model of reciprocating rod seal systems with axial wear texture on rod surface

AbstractIn this paper, a simulation model of reciprocating rod seal systems when there is axial texture on the rod surface due to wear is studied. The model includes macroscopic solid mechanics analysis, microscopic contact mechanics analysis and fluid mechanics analysis, and on this basis, the change of surface pressure when the sealing ring fall into a texture is calculated by the micro‐deformation mechanics analysis of the seal surface. Then, the stiffness matrix method is used to find the film thickness when the three pressures in the sealing area are in equilibrium, completing the fluid–solid coupling calculation. Combined with the above simulation process, the performance parameters of the sealing system such as leakage and friction can be obtained. Results show that axial texture will degrade sealing performance, which increases leakage and friction. The simulation results can quantitative characterise the influence of rod wear on sealing performance and provide some theoretical basis for the study of seal failure mechanism and prediction of seal life.

A Drifter-Based Self-Powered Piezoelectric Sensor for Ocean Wave Measurements.

Recently, piezoelectric materials have received remarkable attention in marine applications for energy harvesting from the ocean, which is a harsh environment with powerful and impactful waves and currents. However, to the best of the authors’ knowledge, although there are various designs of piezoelectric energy harvesters for marine applications, piezoelectric materials have not been employed for sensory and measurement applications in marine environment. In the present research, a drifter-based piezoelectric sensor is proposed to measure ocean waves’ height and period. To analyze the motion principle and the working performance of the proposed drifter-based piezoelectric sensor, a dynamic model was developed. The developed dynamic model investigated the system’s response to an input of ocean waves and provides design insights into the geometrical and material parameters. Next, finite element analysis (FEA) simulations using the commercial software COMSOL-Multiphysics were carried out with the help of a coupled physics analysis of Solid Mechanics and Electrostatics Modules to achieve the output voltages. An experimental prototype was fabricated and tested to validate the results of the dynamic model and the FEA simulation. A slider-crank mechanism was used to mimic ocean waves throughout the experiment, and the results showed a close match between the proposed dynamic modeling, FEA simulations, and experimental testing. In the end, a short discussion is devoted to interpreting the output results, comparing the results of the simulations with those of the experimental testing, sensor’s resolution, and the self-powering functionality of the proposed drifter-based piezoelectric sensor.

Searching for the most optimum burnable absorbers (BAs) for AP-1000 from the neutronic, thermal-hydraulic, and solid mechanics points of view

Because of the importance of absorber materials in regulating the reactivity of AP-1000, several materials with varied designs have been investigated to find the most optimum absorber materials from the neutronic, thermal-hydraulic, and solid mechanics perspectives. In this work, ZrB2, Er2O3, (SiO2-B2O3) and (Al2O3-B4C) were investigated as burnable absorbers (BAs) and H3BO3, Ag–In–Cd, and SS-304 as non-burnable absorbers. For the investigated BAs, the main neutronic parameters such as the fuel burn-up, axial thermal neutron flux distribution and the pin by pin distribution have been simulated. For the non-burnable absorbers, the control rod worth (CRW) and the boron concentration coefficient have been calculated. In the thermal-hydraulic analysis, the temperature distribution of the fuel, clad, coolant and the minimum departure from nucleate boiling ratio (MDNBR) have been studied. The BAs’ effects on solid mechanics analysis have emerged on both the von-Mises stress and the maximum fuel outer surface displacement.

Uncertainty analysis in solid mechanics with uniform and triangular distributions using stochastic perturbation-based Finite Element Method

In this paper theoretical formulation and computational implementation of the Stochastic perturbation-based Finite Element Method (SFEM) for uncertainty analysis in solid mechanics with symmetric non-Gaussian input parameters are presented. Theoretical foundations of the method are based on the general order Taylor expansions of all uncertain input parameters and state functions including even orders only. The first four probabilistic characteristics of the structural responses have been derived for symmetrical triangular and uniform probability distributions of random input including probability distribution truncation effect. The Stochastic Finite Element Method implementation has been completed for the displacement version of the FEM using statistically optimized nodal polynomial response bases, and their coefficients are determined using the Least Squares Method using the weighted and non-weighted schemes. Structural responses of several mechanical systems are analyzed using their basic probabilistic characteristics, which have been validated using the probabilistic semi-analytical approach, and also the crude Monte-Carlo simulation. A relatively good coincidence of three probabilistic numerical techniques confirms the applicability of the Stochastic perturbation-based Finite Element Method to study boundary and initial problems in mechanics with uncertainties having uniform and/or triangular probability distributions.

Earthquake damage estimation of the Koyna concrete gravity dam using explicit GFVM model considering fluid–structure interaction

In this paper, an Explicit Galerkin Finite Volume Method (E-GFVM) is employed to estimate damage paths in concrete structures through the definition of nonlinear behavior of concrete. Furthermore, to verify the accuracy and efficiency of the present method, the E-GFVM outcomes are compared with the Explicit Finite Element Method (E-FEM) which is a well-known numerical method for investigating numerous solid mechanics problems. Due to the essence of explicit methods, the method in question uses a few matrix operations in nonlinear analysis, so it diminishes computation workloads for time-dependent cases with small time-step. The reason for using E-GFVM was its simplicity and high accuracy in estimating stresses and displacements for the analysis of Computational Solid Mechanics (CSM) problems. Furthermore, one important feature of FVM is its local conservation properties which guarantee the global conservation of variables that provides more stability, particularly in dealing with complex problems. To model the nonlinear behavior of concrete, the two equivalent uniaxial stress–strain relations, taking into consideration the softening and hardening behavior in both compression and tension, are implemented in the proposed numerical method. In other words, the bi-axial concrete behavior is defined by applying the idea of current strength in principal stress space. Therefore, this study aims to introduce a new numerical method that in addition to reducing time consumption, can maintain the accuracy of the results. For reaching this purpose, first, the nonlinear behavior of concrete is modeled and two different specimens are placed under pure pressure and tension loads. The results calculated by the E-GFVM are compared with other literature. After verification of the nonlinear behavior of concrete using E-GFVM, the ability of the proposed method for analysis of a real-world case under time-dependent conditions, namely Koyna concrete gravity dam which experienced a destructive earthquake in 1967, is tested, considering the impacts of dam–reservoir interaction. Then, this problem with the same conditions is modeled and analyzed using the E-FEM. The results show that, in spite of good harmony between two utilized methods for estimating the damage on the body of Koyna dam, the CPU time of the E-GFVM became about 3 times less than the E-FEM.

Investigating the possible advantage of using LM bonded gap instead of helium in Ap-1000 nuclear power reactor

This work focuses on the viability of using liquid metal bonded gap instead of the traditional helium (He)-gap through investigating its effects on the neutronic, thermal–hydraulic, and solid mechanics analyses. The shortcoming of using a He-gap is the high thermal resistance of helium, which causes overheating and much heat accumulation inside the fuel, and hence causes many problems with the fuel‘s solid mechanics behavior. To reduce both the heat accumulation and overheating inside the fuel material, LM boned gap was applied. The obtained results showed a slight difference in the various neutronic parameters, while in the thermal–hydraulic analysis, an excellent enhancement in the maximum fuel temperature happened, which reduced the heat accumulation in the fuel material. Also, in solid mechanics analysis, the enhancement that came from decreasing the fuel temperature decreased both the thermal expansion of the fuel and the von-Mises stress that acts on it.

Investigating the neutronic, thermal-hydraulic, and solid mechanics analysis for AP-1000 nuclear reactor

ABSTRACT This study investigates the neutronic, thermal-hydraulic, and solid mechanics analyses for one of the central fuel assemblies with 2.35% U235 enrichment in the AP-1000 Reactor. MCNPX 2.7 computer code, which depends on a Monte Carlo algorithm, was applied to perform the neutronic calculations. Both COMSOL-Multiphysics, based on the numerical solution for the centered rod sub-channel model, and MATLAB, based on the analytical solution for the same model, were applied to perform the thermal-hydraulic analysis. COMSOL-Multiphysics was used to perform the solid mechanics analysis. The neutronic, thermal hydraulics, and solid mechanics analyses play an essential role in the control, design, and safety of nuclear reactors. The calculations of criticality, reactivity, fuel burn-up, neutron flux, and power mapping were performed.‎ From the power mapping, the hot channel was determined and its maximum PPF. Upon getting the maximum PPF, which occurred in channel number 30 and equals 1.357, the thermal-hydraulic calculations using both COMSOL-Multiphysics and MATLAB were applied to determine the temperature distribution of the fuel, clad, and coolant. The departure from nucleate boiling ratio (DNBR) distribution was calculated to determine the minimum departure from ‎nucleate boiling ratio (MDNBR). The MDNBR results were 2.154 based on the analytical approach and 2.20 based on ‎the numerical approach. These values are higher than the limiting value of 1.75, which assure that no nucleate boiling ‎problems will occur. The solid mechanics calculations were investigated by coupling three kinds of physics using COMSOL-Multiphysics (the heat transfer in solid physics to perform the thermal load, turbulence flow RANS K-OMEGA to perform the pressure load, and solid mechanics physics). This coupling was used to determine the von-Mises stress, volumetric strain, and the total displacement for both the fuel and the clad material. The total fuel outer surface displacement was calculated to assure that no surface contact would happen between the ‎fuel and clad material to avoid chemical interactions between them. The displacement was calculated to be 0.007 mm, which is less than the He-gap ‎thickness, 0.008 mm. The coupling between different physics is one of the most well-developed techniques used for simulating the exact situation inside nuclear reactors. This coupling was done using the computational fluid dynamics (CFD) approach. All the calculations for the benchmark problem (a single fuel Assembly (G-9), near Beginning of Life, hot Full Power, equilibrium Xenon, and unrodded Core) were conducted. The obtained results were within the safety limits outlined in the design control document (DCD). Eventually, the results were in line with earlier efforts that utilized different codes for simulating neutronic analysis.

Integrated analysis of VVER-1000 fuel assembly fueled with accident tolerant fuel (ATF) materials

This paper presents an integrated study about some accident-tolerant fuels compared to the standard fuel in trying to find an alternative fuel that enhances the safety, competitiveness, and economics of commercial nuclear power. The neutronic, thermal–hydraulic and solid mechanics analysis of Uranium Nitride (UN) and Uranium Carbide (UC) were performed in a single fuel assembly of the VVER-1000 nuclear power reactor and compared with that of Uranium dioxide (UO2). MCNPX 2.7 computer code and COMSOL-Multiphysics computer software were used to make a deep analysis for the investigated fuel types. In the neutronic analysis, the fuel burn-up, the safety parameters and the power peaking factor (PPF) for the hot channel were simulated. The thermal–hydraulic and solid mechanics analyses were performed on the hot channel to make sure that the maximum temperature of the clad and the coolant would not exceed the safety limits.

Thirty Years of the Finite Volume Method for Solid Mechanics

Since early publications in the late 1980s and early 1990s, the finite volume method has been shown suitable for solid mechanics analyses. At present, there are several flavours of the method, which can be classified in a variety of ways, such as grid arrangement (cell-centred vs. staggered vs. vertex-centred), solution algorithm (implicit vs. explicit), and stabilisation strategy (Rhie–Chow vs. Jameson–Schmidt–Turkel vs. Godunov upwinding). This article gives an overview, historical perspective, comparison and critical analysis of the different approaches where a close comparison with the de facto standard for computational solid mechanics, the finite element method, is given. The article finishes with a look towards future research directions and steps required for finite volume solid mechanics to achieve more widespread acceptance.

An innovative method for surmounting the constrained torsional problems of stocky beams with arbitrary noncircular cross-sectional shapes and with arbitrary elastic material properties

The constrained torsion problems of stocky beams, being still an unsurmountable challenge in solid mechanics, will be solved by the innovative method proposed, and the computational results of numerical examples signifying that the beam model proposed is reasonable and the numerical analysis methodology of nodal line method is effective. The creative cruxes are as followings:•a type of innovative beam model—stocky beam in solid mechanics analysis is defined, which uses the stress state of the beam to distinguish whether a structural member is a beam or not, and the axis of the stocky beam is the locus of the minimum torsional stiffness centre of all its cross sections;•the warpages of all cross sections of a stocky beam are depicted as a mathematical expression that signifies a family of curved surfaces evolved from Prandtl's membrane shapes;•the constrained torsion problem of a stocky beam can be transformed into the boundary value problem of a set of ordinary differential equations by using the nodal line method developed.

Block subspace projection preconditioned conjugate gradient method in modal structural analysis

This paper considers the preconditioned block conjugate gradient method for solving the algebraic, generalized partial eigenvalue problem, which arises when the finite element method is applied to dynamic analysis in structural and solid mechanics. The focus is on the development of an algorithm that keeps constant the iterable subspace dimension, independently of the number of eigenpairs required. Novelties in this approach include a preconditioning strategy based on block incomplete factorization of the shifted stiffness matrix, and analysis of unremovable errors, which accumulate with increasing numbers of eigenpairs.